One of the most powerful approaches to drug discovery today is the use of an X-ray crystal structure of the target protein. Termed structure based drug design (SBDD), this approach can accelerate the drug discovery process allowing drugs to reach the market place years sooner. At present, no G-Protein Coupled Receptor (GPCR) X-ray crystal structure has been accomplished. The first major obstacle in GPCR structure determination is the availability of milligram quantities of pure protein. We propose to eliminate this bottleneck through the development of a generally applicable expression and purification system for integral membrane proteins. Specifically, we will use the therapeutically relevant glucagon receptor (GGR) as a model to produce and purify milligrams of active receptor. Extensive protein engineering will be used to produce a protein amenable to crystallization. This will include genetically engineered fusions and truncations. Produced protein will be used to initiate crystallization trials. An X-ray crystal structure of GGR would have a major impact on the design of new pharmaceuticals for the treatment of diabetes and related diseases. PROPOSED COMMERCIAL APPLICATIONS: Drugs that target integral membrane proteins represent greater than 30% of the top selling pharmaceuticals with total annual sales exceeding $60 billion. The proposed research will have a significant impact on the discovery of ethical pharmaceuticals that target membrane proteins. At present, structure-based drug design approaches for G-protein coupled receptor targets are not feasible. This proposal provides an enabling solution to achieving structures of G-protein coupled receptors.